In recent years, many image forming apparatuses of electronic photography type are utilized such as printer, facsimile apparatus, copying apparatus, multiplex apparatus and the like. As such apparatus, it has an image formation composed of respective processes of charging, exposing, developing, transferring, fixing and cleaning. In these processes, developing process is to use a developing device to make developing roller serving as developer carrying body carry developer (i.e. toner) so as to perform a development of electrostatic latent image with respect to photosensitive drum serving as an electrostatic latent image carrying body.
In such developing device, besides the developing roller, a supplying roller for supply toner to the developing roller, and a toner stirring unit for stirring toner as developer stirring unit are furnished.
FIG. 16A is a first explanatory diagram showing a conventional toner stirring unit; and FIG. 16B is a second explanatory diagram showing a conventional toner stirring unit.
A toner stirring unit 100, as shown by FIG. 16A, includes a toner hopper 102 for accommodating toner 101 as accommodating tank; a stirring bar 103 as stirring member; and a driving section 104. The stirring bar 103 has a built-in magnet 105; and is supported to freely rotate by a supporting pivot 106 in the toner hopper 102. On one end of the supporting pivot 106, a projection portion 106a is formed, the driving section 104 presses the projection portion 106a to make the supporting pivot 106 and the stirring bar 103 rotate along a direction of arrow “A”. Further, under the toner hopper 102, a magnetic sensor 107 is furnished which can detects strength of magnetic field coming from the magnet 105.
When a rotation force is transferred from a driving unit (not shown) so that the driving section 104 rotates, the stirring bar 103 rotates together with the supporting pivot 106, after its tip rotated to an uppermost position i.e. an upper dead point position, the stirring bar 103 rotates to drop quicker than the driving section 104 through its own weight. Then, as shown by FIG. 16A, the stirring bar 103 stops on the toner 101 accommodated in the toner hopper 102. At that time, a control circuit (not shown) judges a stop position of the stirring bar 103 so as to judge a remainder amount of the toner 101 in the toner hopper 102, on the basis of the strength of magnetic field detected by the magnetic sensor 107. It may refer to Patent Document 1.
Patent Document 1: Japan patent publication of No. Heisei 09-054488.
However, in such conventional toner stirring unit 100, in the case that the remainder amount of the toner 101 in the toner hopper 102 becomes little, as shown by FIG. 16B, the stirring bar 103 produces rebound or vibration when dropping to the toner 101. Therefore, there is problem that the remainder amount of toner could not be correctly judged.